Method and device to determine the aerodynamic diameter of particles

Abstract

The invention concerns a method and device for determining the aerodynamic diameter of particles carried in a flow. To that end, the velocity of the flow is altered in an area and the particle velocity measured at at least one point before said area and at at least one point in or after said area. Owing to the alteration of the flow velocity, the particles carried in the flow are with increasing aerodynamic diameter retarded or accelerated increasingly more slowly than the carrier fluid, depending on whether an area of flow retardation or flow acceleration is concerned. Knowing the constraints makes it possible, therefore, by measuring the particle velocity in or shortly after this area of altered flow velocity, to infer the aerodynamic diameter. Correlating the particle velocity data thus obtained with the as well performed particle velocity measurement before the area of flow velocity alteration, where all of the particles of different size still have approximately the same velocity, allows determining the aerodynamic diameter independently of the inflow velocity of the particle-laden flow. Hence, a device basing on the method can be installed directly in a technical circulation, which enables "in-situ" measurements of the aerodynamic diameter of particles.

Claims

1. Method for determining the aerodynamic diameter of particles carried in a flow, comprising the steps of:

altering the flow velocity of the particles in an area;

measuring a first particle velocity at at least one point in or after said area;

measuring a second particle velocity at a point before said area; and

determining the aerodynamic diameter of particles based on the first and second measured particle velocities.

2. Method according to claim 1, wherein said method is carried out "in-situ."

3. Method according to claim 1, wherein said altering step comprises passing the flow through a closed conduit and altering the velocity of the flow by altering the cross section of the conduit.

4. Device for determining the aerodynamic diameter of particles carried in a flow, comprising:

a conduit having a design that changes the flow velocity, said conduit having a first area associated with a first particle velocity and a second area associated with a second particle velocity; and

a measuring system capable of measuring particle velocities at at least two points in the field of flow, one of said two points disposed in said first area, another of said two points disposed in said second area.

5. Device according to claim 4, wherein said conduit includes two different cross sections.

6. Device according to claim 4, wherein said conduit includes an open flow area with areas of one of flow retardation and flow acceleration.

7. Method according to claim 1, wherein said measuring steps comprise measuring the particle velocity using one of optical and laser-optical metrology methods.

8. Method according to claim 7, wherein said measuring steps comprise measuring particle velocity by one of laser-doppler anemometry and laser dual-focus anemometry.

9. Method according to claim 7, wherein said measuring steps comprise measuring particle velocity using light beam measuring methods.

10. Device according to claim 4, wherein said measuring system uses optical or laser-optical metrology methods.

11. Device according to claim 10, wherein said measuring system uses one of laser-doppler anemometry and laser dual-focus anemometry methods.

12. Device according to claim 11, wherein said measuring system uses light beam measuring methods.